1. Field of the Invention
This invention relates generally to data communication systems and in particular to an improved data signalling system particularly well adapted for use in multiple unit radio communication systems capable of voice and data communications.
2. Description of the Prior Art
In the prior art, multiple unit radio communications systems utilize complex signalling systems to provide both voice and data communications capability. Some provide one way status indication capability and acknowledge but with very inflexible formats which limit usefulness. In addition, existing systems utilize structures which are very expensive to manufacture and provide for limited sensitivity in most RF environments. Further, previous systems have been organized around a coding structure that viewed the terminal device as one which responded to a set of discrete commands. The terminal was designed to perform some arbitrary set of operations when a defined command code activated it. This resulted in an inflexible system.